The purpose of this project is to obtain sufficient amino acid sequence analysis from pathogenic bacterial surface membrane proteins to facilitate isolation of the corresponding genes using synthetic oligonucleotide mixtures. The genes will then be sequenced by dideoxynucleotide or Maxim-Gilbert methods, and some will be evaluated for use in vaccines. Several milligrams of the serotype specific proteins (SSPs) (formerly called PIs) from Borrelia hermsii have been isolated by selective detergent extraction followed by reverse phase HPLC. Both the type 7 and type 21 SSPs have blocked amino termini. Cyanogen bromide cleavage of the SSPs and analysis of the fragments by automated Edman degradation and Western blot analysis indicate (l) each B. hermsii SSP represents a different gene product and (2) there is sufficient regions of sequence homology between these SSPs to indicate that they evolved from a common ancestral gene. These observations suggest that the SSPs in B. hermsii represent the first large bacterial multigene family identified to date and provide an excellent model to study gene activation in bacteria at the molecular level. Clones from Chlamydia trachomatis LGV-2 have been selected using a synthetic oligonucleotide made to residues 12-16 of the major outer membrane protein (MOMP). DNA sequence analysis has generated approximately 1 Kb of information from a 5-Kb fragment, but the nucleotide sequence corresponding to the MOMP amino terminus has not yet been located.